s 

595 



SOIL FERTILITY 
LABORATORY MANUAL 

HOPKINS * PETTIT 




Class Sj^3 

Book iLl- 

Gopyiightl^? 

COPYRIGHT DEPOSIT. 



SOIL FERTILITY 
LABORATORY MANUAL 



BY 

CYRIL G. HOPKINS, Ph.D. 

PROFESSOR OF AGRONOMY IN THE UNIVERSITY OF ILLINOIS 



JAMES H. PETTIT, Ph.D. 

ASSISTANT PROFESSOR OF SOIL FERTILITY IN THE UNIVERSITY OF ILLINOIS 



GINN AND COMPANY 

BOSTON • NEW YORK • CHICAGO • LONDON 



s^ 



(?['^ 



wA 



COPYRIGHT, 1910, BY 
CYELL G. HOPKINS and JAMES H. PETTIT 



ALL RIGHTS RESERVED 
310.7 



VChe iatftengnm gregg 

GTNN AND COMPANY • PRO- 
PRIETORS • BOSTON • U.S.A. 



©CLA2711': 



PREFATOEY NOTE 

The student practices described in this laboratory manual are the 
result of ten years' experience by the authors in conducting classes 
in a course of study in soil fertility. With some modifications the 
usual chemical methods are employed, specific chemical directions 
being commonly based upon those adopted by the Association of 
Official Agricultural Chemists. Otherwise these practices were origi- 
nated in this University. 

The increasing number of students in this institution, and the 
fact that some other institutions also use our manual, induced us 
to put it in printed form. 

Suggestions from other teachers of soil fertility regarding pos- 
sible improvements in the manual will be gladly received. 

THE AUTHORS 

University of Illinois, Urbana 



TABLE I 

Elements, Symbols, and International Atomic Weights 
FOR 1910 



Name 


Symbol 


Atomic 
Weight 


Name 


Symbol 


Atomic 
Weight 


Aluminum 


Al 


27.1 


Lead (Plumbum) . . . 


Pb 


207.1 


Antimony (Stibium) . . 


Sb 


120.2 


Lithium 


Li 


7.0 


Argon 


A 


39.9 


Magnesium 


Mg 


24.8 


Arsenic 


As 


75.0 


Manganese 


Mn 


54.9 


Barium 


Ba 


137.4 


Mercury (Hydrargyrum) 


Hg 


200.0 


Bismuth 


Bi 


208.0 


Molybdenum .... 


Mo 


96.0 


Boron 


B 


11.0 


Nickel 


Ni 


58.7 


Bromin 


Br 


79.9 


Nitrogen 


N 


14.0 


Cadmium 


Cd 


112.4 


Oxygen 





16.000 


Calcium 


Ca 


40.1 


Phosphorus .... 


P 


31.0 


Carbon 


C 


12.0 


Platinum 


Pt 


195.0 


Chlorin 


CI 


35.5 


Potassium (Kalium) . . 


K 


39.1 


Chromium 


Cr 


52.0 


Silicon 


Si 


28.3 


Cobalt 


Co 


59.0 


Silver (Argentum) . . 


Ag 


107.9 


Copper (Cuprum) . . . 


Cu 


63.6 


Sodium (Natrium) . . 


Na 


23.0 


Pluorin 


r 


19.0 


Strontium 


Sr 


87.6 


Gold (Aurum) .... 


Au 


197.2 


Sulfur 


S 


32.1 




H 


1.008 


Tin (Stannum) . . . 


Sn 


119.0 


lodin 


I 


126.9 


Titanium 


Ti 


48.1 


Iron (Ferrum) .... 


Fe 


55.9 


Zinc 


Zn 


65.4 



TABLE II 
Nitric Acid in Solutions of Different Specific Gravity at 15° C. 



Specific 


Grams HNO3 


Specific 


Grams HNO3 


Specific 


Grams HNO3 


Gravity 


in 100 cc. 


Gravity 


IN 100 cc. 


Gravity 


IN 100 cc. 


1.09 


16.9 


1.23 


45.2 


1.37 


81.4 


1.10 


18.8 


1.24 


47.5 


1.38 


84.6 


. 1-11 


20.7 


1.25 


49.8 


1.39 


87.9 


1.12 


22.7 


1.26 


52.1 


1.40 


91.4 


1.13 


24.6 


1.27 


54.4 


1.41 


95.2 


1.14 


26.6 


1.28 


56.8 


1.42 


99.1 


1.15 


28.6 


1.29 


59.3 


1.43 


103.2 


1.16 


30.6 


1.30 


61.7 


1.44 


107.5 


1.17 


32.6 


1.31 


64.3 


1.45 


112.1 


1.18 


34.7 


1.32 


66.9 


1.46 


116.8 


1.19 


36.7 


1.33 


69.7 


1.47 


121.9 


1.20 


38.8 


1.34 


72.5 


1.48 


127.4 


1.21 


40.9 


1.35 


75.3 


1.49 


133.5 


1.22 


43.0 


. 1.36 


78.3 


1.50 


141.1 



TABLE III 

Ammonia in Solutions of Ammonium Hydroxid of Different Specific 

Gravity at 15° C. 



Specific 


Grams NH3 in 


Specific 


Grams NH3 in 


Specific 


Grams NH3 in 


Gravity 


100 cc. 


Gravity 


100 cc. 


Gravity 


100 cc 


.940 


14.69 


.920 


20.01 


.900 


25.50 


.938 


15.21 


.918 


20.56 


.898 


26.05 


.936 


15.74 


.916 


21.09 


.896 


26.60 


.934 


16.27 


.914 


21.63 


.894 


27.15 


.932 


16.81 


.912 


22.19 


.892 


27.70 


.930 


17.34 


.910 


22.74 


.890 


28.26 


.928 


17.86 


.908 


23.29 


.888 


28.86 


.926 


18.42 


.906 


23.83 


.886 


29.46 


.924 


18.93 


.904 


24.39 


.884 


30.14 


.922 


19.47 


.902 


24.94 


.882 


30.83 



TABLE IV 

Hydrochloric Acid in Solutions of Different Specific 
Gravity at 15° C. 



Specific 


Grams HCl in 


Specific 


Grams HCl in 


Specific 


Grams HCl in 


Gravity 


100 cc. 


Gravity 


100 cc. 


Gravity 


100 cc. 


1.040 


8.5 


1.095 


20.9 


1.150 


34.0 


1.045 


9.6 


1.100 


22.0 


1.155 


35.3 


1.050 


10.7 


1.105 


23.2 


1.160 


36.6 


1.055 


11.8 


1.110 


24.3 


1.165 


37.9 


1.060 


12.9 


1.115 


25.5 


1.170 


39.2 


1.065 


14.1 


1.120 


26.7 


1.175 


40.4 


1.070 


15.2 


1.125 


27.8 


1.180 


41.8 


1.075 


16.3 


1.130 


29.1 


1.185 


43.0 


1.080 


17.4 


1.135 


30.3 


1.190 


44.3 


1.085 


18.6 


1.140 


31.5 


1.195 


45.6 


1.090 


19.7 


1.145 


32.8 


1.200 


46.9 



VI 



LIST OF APPARATUS 



1 Double condenser with connecting 

tubing 

2 Ring stands 

6 Rings, 4 sizes 

3 Iron gauze with asbestos center 

2 Safety distillation bulbs 

3 Pinchcocks 

4 Rubber stoppers 

2 Triangles, pipestem 
2 Erlenmeyer flasks, 200 cc. 
2 Erlenmeyer flasks, 300 cc. 
4 Beakers, Jena, 250 cc. 
4 Beakers, Jena, 400 cc. 
2 Crucibles, 14 cc. 
2 Crucibles, 25 cc. 
4 Funnels, 6 cm. 
2 Funnels, 10 cm. 

1 Crucible tongs 

2 Evaporating dishes, 8 cm. 
2 Evaporating dishes, 10 cm. 
1 Graduated cylinder, 25 cc. 
1 Graduated cylinder, 100 cc. 
1 Graduated pipette, 25 cc. 

1 Pipette, 25 cc. 
1 Pipette, 10 cc. 

1 Burette, 50 cc. 

2 Test tubes 

2 Watch glasses, 10 cm. 



1 Camel's-hair brush 
1 Measuring flask, 250 cc. 
1 Measuring flask, 500 cc. 
1 Bone spoon 
1 Forceps 

1 Thermometer, 100° 

2 Bunsen burners with connecting 

tubing 
1 Adjustable burner with connecting 

tubing 
1 Burette clamp 

1 Apparatus clamp 

4 Kjeldahl flasks, 500 cc. 

2 Bottles, 250 cc. 
2 Bottles, 500 cc. 
2 Bottles, 1000 cc. 

1 Bottle, 2500 cc. 

2 Wash bottles, Jena, 1000 cc. 
1 Desiccator, 12 cm. diameter 

3 Percolators, 1000 cc. capacity 

4 Stirring rods 

1 Screw clamp 

2 Quart jars 

1 Rubber policeman 

1 Weighing pan 

2 Iron crucibles of about 100 cc. ca- 

pacity, with covers 



PRACTICE I 

PREPARATION OF STANDARD HYDROCHLORIC ACID 
SOLUTION 1 

By the use of a hydrometer and the specific-gravity table prepare 
5 liters or more of approximately one half normal hydrochloric acid, 
using chemically pure concentrated acid and ammonia-free water. 

Standardize by the silver nitrate method : Place exactly 25 cc. 
(note temperature of stock solution when measured out) of the acid 
solution, measured with a pipette, in a 300-cc. Erlenmeyer flask, 
dilute to 75 cc, and add at once from a burette sufficient 5 per cent 
silver nitrate solution to nearly, but not quite, precipitate all the 
chlorin. Close the flask with a clean rubber stopper and shake till 
the precipitate will settle almost completely in a short time. Then 
add the silver nitrate in 1-cc. portions, shaking after each addition, 
until the precipitation is complete, avoiding more than 1 cc. excess 
of silver nitrate solution. 

Shake until the silver chlorid settles well, wash three times by 
decantation (after shaking each time), using about 100 cc. of water 
containing 1 cc. concentrated nitric acid per liter, and decanting the 
liquid through a 9-cm. filter. Transfer the precipitate to the filter, 
dry, transfer the bulk of the precipitate to a watch glass or crucible, 
and burn the paper in a weighed crucible. Add 2 to 5 drops of 
concentrated nitric acid to dissolve reduced silver, and then add 2 to 
5 drops of concentrated hydrochloric acid. Evaporate to dryness 
without spattering, add the main precipitate, dry to constant weight 
at 120° to 130°, cool in a desiccator, and weigh. 

Record the weights of silver chlorid from duplicate 25-cc. portions 
of the standard hydrochloric acid. 

^ To be done by the instructor. 



PRACTICE II 

PREPARATION OF A STANDARD AMMONIA SOLUTION 

Determine, by hydrometer, the specific gravity of concentrated 
ammonia, and calculate, by the use of the specific-gravity table, 
the number of cubic centimeters necessary to make 2 liters of ap- 
proximately one fifth normal ammonia solution. 

Sp-gr 

Grams NHg per cc 

Grams NHg per liter in normal solution.... 

Grams NHg in 2 liters of 1-5 normal solution 

No. of cc. of cone. NHg equivalent to g. NHg 



Measuj-e out the required amount of concentrated ammonia, add 
water to make the total volume up to 2 liters, and mix thoroughly. 
Standardize by titrating 10 cc. of the standard hydrochloric acid 
with the ammonia solution, using lacmoid as an indicator. Make 
three titrations : 

(1) 10 cc'. HCl is equivalent to cc. NHg 

(2) 10 cc. HCl is equivalent to cc. NHg 

(3) 10 cc. HCl is equivalent to cc. NHg 

Av cc. NHg 

1 cc. NHg is equivalent to mg. N. 

Grive reactions in first and second practices, and record the com- 
putations involved in ascertaining the weight of nitrogen in 1 cc. 
of the standard ammonia solution. 



PRACTICE III 

BLANK DETERMINATION OF NITROGEN IN REAGENTS 
USED IN DISTILLING 

Place 250 cc. of ammonia-free water in a Kjeldahl flask and con- 
nect latter in the distillation apparatus shown in the figure on the 
opposite page. Arrange the 300-cc. Erlenmeyer flask K, contain- 
ing 10 cc. of the standard hydrochloric acid and about 15 cc. of 
ammonia-free water, so that the end of the delivery tube / dips into 
the solution. By disconnecting at D and inserting a funnel in the 
rubber tube, bring 10 cc. of an alkali solution (1000 g. Greenbank 
alkali and 25 g. potassium sulfid in 1000 cc. water) into the Kjeldahl 
flask. Close the pinchcock E, shake the flask thoroughly, and con- 
nect with the steam generator C Open the pinchcock E and close 
A, thus forcing steam through the flask and carrying the liberated 
ammonia over into the standard acid. Heat the. Kjeldahl flask suffi- 
ciently to prevent condensation of the steam. Distil to a volume of 
200 cc, add lacmoid, and titrate with the standard ammonia solution. 

(1) Titration cc. NHg 

(2) Titration : cc. NHg 

Av. '. cc. jSTHg 

State correction in cubic centimeters of standard ammonia solution. 
What does this mean, and how is it to be used ? 




Fig. 1. Distillation Apparatus for the Nitrogen Determination 

The apparatus shown in Fig. 1 has been found very convenient in student labora- 
tories. C is a liter flask to be used as a steam generator. Its rubber stopper carries 
the glass tube B, which acts as a safety valve; a second glass tube, on the end of 
which is a piece of rubber tubing and the pinchcock A ; and a third glass tube, con- 
necting, by means of the rubber tubing D, with the glass tube F. The latter goes 
nearly to the bottom of the Kjeldahl flask G, which is connected with the block- 
tin tube of the condenser / through the Hopkins safety distillation bulb H. K is a 
receiving flask containing the standard acid. By means of a Y-tube in place of the 
third glass tube in the stopper of C, two Kjeldahl flasks for duplicate determinations 
may be connected with the latter 



PRACTICE IV 

DETERMINATION OF NITROGEN IN REAGENTS 

Measure out exactly 10 cc. of the concentrated alkali in a beaker 
and dilute to 200 cc. with distilled water. Stir and add slowly, finally 
drop by drop, concentrated sulfuric acid until the alkali is neutral- 
ized, as shown by the change of color. 

10 cc. alkali are equivalent to cc. HgSO^ 

How many cubic centimeters of alkali are necessary to neutralize 
20 cc. H2SO4? 

Place approximately 2 g. of pure sugar in a Kjeldahl flask, add by 
measure approximately .65 g. metallic mercury and 20 cc. sulfuric acid. 
Digest in a ventilated hood over a low flame till colorless, and while 
still boiling hot carefully add powdered potassium permanganate 
until the solution is green. Allow to cool. Add 200 cc. of ammonia- 
free water, connect in the distillation apparatus, add carefully suffi- 
cient concentrated alkali to neutralize 20 cc. of concentrated sulfuric 
acid, shake until thoroughly mixed, and distill, using 10 cc. of 
standard acid in the receiver. 

(1) Titrations '. cc. NHg 

(2) Titrations cc. NH3 

Av cc. NH3 

Check up the standard ammonia solution by titrating against the 
standard hydrochloric acid solution. 

Correction for nitrogen in reagents in terms of standard ammonia 
solution cc. 

Explain the use of the sugar. Give the reaction between the sugar 
and the sulfuric acid. Why is the mercury used '? the potassium per- 
manganate ? the potassium sulfid ? 




Fig. 2 



Fig. 2 shows more in detail the condenser of the distillation apparatus and the way in 
which it is supported. It consists of a rectangular galvanized-iron box (16" X 6" X 3"), 
through which pass two block-tin tubes L, L. N is the inlet and P the outlet for 
the condensing water. It is supported by the ring Q of an iron stand, through which 
passes the projection M. The holes in the right-angled pieces 0, allow the rod of 
the iron stand to pass through readily. 



PRACTICE V 



DETERMINATION OF NITROGEN IN FARM PRODUCE 



Each group of students will work upon one of the following 
materials : ^ 

1. Wheat. 5. Oats. 

2. Com. 6. Oat straw. 

3. Corn stover. 7. Red-clover hay. 

4. Corncobs. 8. Alfalfa. 

Weigh out exactly 2 g. of the material numbered with your group 
number and determine the nitrogen in it according to the method 
given in Practice IV. 

Titrations , cc. NHg 

Titrations cc. NHj 

Av cc. jSTHg 

Per cent N 

Pounds per ton 

Calculate the results obtained, and with these record the results 
obtained by three members of each group as indicated upon the 
following page, valuing nitrogen at 15 cents per pound. How many 
tons of red clover must be plowed under in order to supply in this 
way the nitrogen for a 100-bushel crop of corn and a 100-bushel 
crop of oats in a corn, oats, and clover rotation ? 

Compute the pounds of nitrogen required to produce the crops 
given in the table below. Compute the weight of sodium nitrate 
(95 per cent pure) which would supply the nitrogen found in these 
crops, and the cost of the same. 



Kind of Produce 


Pounds N in 
Produce 


Pounds NaNOj 
Equivalent 


Cost of 
NaNO.T 


(1) 100 M. shelled corn 








(2) 1000 lb. cobs 








(3) Stover, weight equal to (l) + (2) . 








(4) 100 bu. oats 








(5) 5000 lb. oat straw 








(6) 4 tons clover hay 








Total for three crops . . . 









1 These or other stock materials of large importance in agriculture should he 
furnished hy the laboratory in finely pulverized, air-dry condition. The student is 
encouraged to determine nitrogen in some other produce which may be of special 
local interest in his home community. 

10 



PRACTICE V (Continued) 



Name of Student 


Kind of Produce 


Per Cent N 


N IN One Ton 


Pounds 


Value 
































Average 






































Average 






































Average 












i 


























Average 






































Average 








• 






























Average 






































Average 






































Average 









11 



PRACTICE VI 

DETERMINATION OF NITROGEN IN SOILS 

Each group of students will work upon one stock soil, such as the 
following : ^ 

1. Surface of gray silt loam. 5. Surface of black clay loam. 

2. Subsoil of gray silt loam. 6. Subsoil of black clay loam. 

3. Surface of brown silt loam. 7. Sandy soil. 

4. Subsoil of brown silt loam. 8. Peaty soil (use 2 g.). 

For all soils except peat weigh out 10 g. of air-dry soil and use 
10 cc. of standard hydrochloric acid in the receiver. 

(1) Titration cc. NHg 

(2) Titration cc. NHg 

Av cc. NHg 

Per cent N 

Calculate the results obtained, and with these record the results 
obtained by three ' members of each group as indicated upon the 
following page. 

Assuming that there are 2,000,000 pounds in an acre to the depth 
of 6f inches, how many pounds of nitrogen are there in this plowed 
soil ? How many 100-bushel crops of corn will this produce if the 
total crop is removed ? 

1 These are types of soil which can easily be found in almost every state in the 
North Central group ; but in other sections the important and extensive type soils of 
the state should be substituted for some of these. 



12 



PRACTICE VI (Continued) 



Name of Student 


Kind of Soil 


Per Cent N 


Pounds of N 
IN Two Mil- 
lion OF Soil 


No. OFIOO-BUSHEL 

Crops of Corn 
Equivalent 
































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 









13 



PRACTICE VII 

DETERMINATION OE 'THE REACTION OE A SOIL 

Each group of students will work upon one of a group of soils 
selected by the instructor, using surface and subsoil samples. 

Place about 10 g. of soil in a Jena-glass flask with 100 cc. of 
ammonia-free water, shake thoroughly several times, and allow to 
stand over night. Draw off 50 cc. of the supernatant liquid, add 
a few drops of phenolphthalein, and concentrate in a Jena-glass 
beaker to about 10 cc, if a pink color does not develop before this 
point is reached. 

To what is the development of a pink color in the solution due ? 

What is the condition of the soil when no color appears ? 

If no pink color develops, determine acidity as directed in Prac- 
tice IX. . 

If a pink color develops, determine the limestone present accord- 
ing to directions given in Practice X. 



14 



PRACTICE VIII 

PREPARATION OP STANDARD SODIUM HYDROXID AND NORMAL 
POTASSIUM NITRATE SOLUTIONS i 

These solutions are to be used in the determination of soil acidity. 

1. Weigh out enough sodium hydroxid (sticks, purified over alcohol, 
about 75 per cent NaOH) to make about 3 liters of solution of such 
strength that 1 cc. shall be equivalent to 4 mg. of calcium carbonate. 
Dissolve in ammonia-free water, dilute to exactly 1000 cc, add 100 cc. 
of a saturated barium hydroxid solution, shake well, and allow to stand 
over night, or until clear. Draw off 100 cc. of the clear solution, and 
place in a 250-cc. bottle containing 100 cc. of the saturated solution of 
barium hydroxid. If a precipitate occurs, add the 200 cc. to the main 
solution, shake, and repeat the above operations until no further pre- 
cipitate occurs. (If no precipitate is formed, throw away the 200 cc.) 
Always keep an exact record of the amount of liquid remaining in the 
stock bottle. When the solution is free from carbon dioxid, draw off 
100 cc. and place in a 100-cc. bottle. Fill the burette with this and 
titrate against 10-cc. portions of standard hydrochloric acid. Add 
ammonia-free water so that 1 cc. of the standard .sodium hydroxid 
solution shall be exactly equivalent to 4 mg. of calcium carbonate. 

2. Prepare 5 liters of a normal potassium nitrate solution, assum- 
ing the salt to be pure. 

If 100 g. of an acid soil are placed in 250 cc. of normal potassium 
nitrate solution and shaken for three hours, a reaction takes place 
between the potassium nitrate and the acid constituents of the soil, 
giving, as one of the products, soluble acid salts, and so making the 
acidity determinable. An equilibrium is reached, however, before 
this reaction runs to an end ; and if, after having drawn off 125 cc. 
to titrate, 125 cc. of fresh potassium nitrate are added to the bottle 
and the bottle again shaken for three hours, 125 cc. drawn off will 
give a titration which is more than one half of the first. By continu- 
ing this process until the last 125 cc. shows practically no acidity, 
we have a series of titrations the sum of which represents the total 
acidity of the 100 g. of soil. It has been found by working with a 
number of different soils that, as an average, the sum of such a series 
is two and one-half times the first titration. 

Consequently, when the sodium hydroxid is made up so that 1 cc. 
is equivalent to 4 mg. of calcium carbonate, and 125 cc. (which repre- 
sent 50 g. of soil) are titrated, each 0.1 cc. required to neutralize cor- 
responds to 1 mg. of calcium carbonate required by the 100 g. of soil, 
or to 0.001 per cent of calcium carbonate required by the soil tested. 

1 To be done by the instructor. 

16 



PRACTICE IX 

DETERMINATION OF ACIDITY (OR LIMESTONE REQUIRED)' 

or SOILS 

Place 100 g. of soil in a 400-cc. (or 12-oz.) wide-mouthed bottle, 
add 250 cc. normal potassium nitrate solution, stopper, and shake 
continuously for three hours in a shaking machine, or every five 
minutes by hand. Let stand over night. Draw off 125 cc. of the clear 
supernatant liquid, boil ten minutes to expel carbon dioxid, cool, and 
titrate with the standard sodium hydroxid, using phenolphthalein 
as indicator. 

Surface Subsoil 

(1) Titrations cc. NaOH 

(2) Titrations cc. NaOH 

Av. cc.NaOH 

Per cent CaCOg required 

What crops, and in what way, does ground limestone mainly 
benefit ? 



18 



PRACTICE X 

DETEKMINATION OF THE INORGANIC CARBON (OR LIMESTONE 
PRESENT) IN A SOIL 

Use the apparatus referred to in Practice XXX for organic carbon. 

Place from 2 to 10 g. of soil, according to the amount of carbonates 
present, in the Erlenmeyer flask. Connect with the apparatus and 
bring in slowly through the separatory funnel an excess of dilute 
(1 : 1) hydrochloric acid. After the reaction is over, boil the contents 
of the flask to drive out dissolved carbon dioxid, fill with water 
through the separatory funnel, measure the volume of gas in the 
burette, and pass same into an absorption pipette containing a 33 per 
cent solution of potassium hydroxid. Eeturn the unabsorbed gas to 
the burette and read off its volume. The difference between the 
readings is carbon dioxid, whose volume must be corrected for tem- 
perature and pressure. 

(1) (2) 

cc. of COg 

Barometer and temperature 

Weight of C equivalent 

Weight of CaCOg equivalent 

Per cent of CaCOg present 

Average ' 

Calculate the results obtained in Practices IX and X, and with 
these record the results obtained by three members of each group as 
indicated upon the following page. Consider 6§ acre-inches of normal 
soil to weigh 2,000,000 pounds. 



20 



PRACTICES IX AND X (Continued) 



Name of Student 


Kind of Soil 


CaCOg Required 
Per Cent 


CaCOj Required 

Pounds per 

Acre 


CaCOg Present 

Pounds per 

Acre 




Surface 


Subsoil 


Surface 


Subsoil 


Surface 


Subsoil 


















































Average 






























































Average 






























































Average 






























































Average 






























































Average 






























































Average 






























































Average 
















. 














































Average 















21 



PRACTICE XI 

PREPARATION OF PLANT-FOOD SOLUTIONS i 

Solution No. 1. Nitrogen : Dissolve 80 g. of ammonium nitrate in 
2500 cc. of distilled water. Use 10 cc. per pot. 

Solution No. 2. Phosphorus : Dissolve 25 g. of monocalcium phos- 
phate or 26 g. of disodium phosphate in 2500 cc. of ammonia-free 
water. Use 10 cc. per pot. 

Solution No. 3. Potassium : Dissolve 50 g. ©f potassium sulfate in 
2500 cc. of ammonia-free water. Use 10 cc. per pot. 

Solution No. 4. Magnesium : Dissolve 20 g. of magnesium sulfate 
in 2500 cc. of ammonia-free water. Use 10 cc. per pot. 

Solution No. 5. Iron : Dissolve 0.1 g. ferric chlorid in 250 cc. of 
ammonia-free water. Use 1 cc. per pot. 

Prepare these solutions carefully, using chemically pure salts, and 
label each bottle. 

1 To be done by the instructor. 



22 



PRACTICE XII 

PREPARATION OF POT CULTURES 

Use clean, white, sifted quartz sand in 5-liter heavy glass battery- 
jars, having a 1-cm. hole within 1 cm. of the bottom. Into the hole 
fit a drain tube made of glass tubing with a glass-wool filter at the 
inner end, so that it will drain from the lowest part of the jar. Put 
up a series of eight of these pots, to be used as indicated in the 
table on the following page. 

To extract the sand, fill the jar within 1 cm. of the top with dry 
sifted sand and add to this dilute sulfuric acid (made by adding 
100 cc. of concentrated chemically pure sulfuric acid to 900 cc. of 
ammonia-free water) until the sand is saturated. Let stand two 
hours and then add ammonia-free water, allowing the drainage to 
flow into a second jar until it is saturated. Allow this jar to stand 
two hours and then wash both with ammonia-free water until free 
from acid. 

After drying, mix with the sand of each pot 10 g. of pure calcium 
carbonate. 

In making applications of plant food as indicated in the following 
table, and in such amounts as are shown in Practice XI, bring the 
solutions to be applied to each pot into about 1 liter of water, mix 
thoroughly, and apply the whole amount to the pot, allowing any 
water present to be forced out through the drain. 

The first application of plant food is to be made at the time of 
planting, the second three weeks later, the third two weeks later, 
and subsequent applications at intervals of one week, each time 
making the application as directed above. 

Each student in each group will prepare and care for a series 
of pots, as indicated in the following table. 



24 



PRACTICE XII (Continued) 



Pot 


Preparation of 
Sand 


Plant Food 
Added 


Seeds Planted in Groups 


No. 


1 


2 


3 


4 


5 


6 


7 


8 


1 


Extract and wash 


None 


Corn 


Oats 


Wheat 


Barley 


Buck- 
wheat 


Millet 


Rape 


Flax 


2 


. 


All but N 


u 


u 


u 


" 


u 


11 


u 


a 


3 


11 


All but P 


" 


l( 


" 


u 


" 


" 


" 


it 


4 


" 


All but K 


11 


u 


u 


" 


" 


" 


u 


u 


5 


None 


All 


" 


" 


" 


" 


u 


u 


" 


" 


6 


" 


All 


Red 
Clover 


Cow- 
peas 


Soy 
Beans 


Vetch 


Alfalfa 


Sweet 
Clover 


Crim- 
son 
Clover 


Alsike 
Clover 


71 




All but N 


u 


u 


u 


u 


(1 


u 


u 


(( 


8 


u 


All but N 
Bacteria 2 


(( 


u 


" 


" 


" 


u 


" 


u 



1 In accurate work this pot should be covered with a layer of cotton, heated in an autoclave two hours 
at 125°, and planted with sterilized seed, assisting the young plants to push up tlirough the cotton. 

2 Obtain about 0.5 kg. of soil which has recently grown the infected legume, and shake it up with about 
1 liter of water. Let settle, and with each seed as it is planted add 10 cc. of the supernatant liquid before 
the seed is covered. 

Why is the CaCOs added? Make observations and at least weekly notes of any differences in growth, 
and explain. 



25 



PRACTICE XIII 

PREPARATION OP AN AMMONIUM SULPATE SOLUTION 

Weigh out exactly in a weighed crucible the number of grams of 
chemically pure ammonium sulfate (assuming the salt to be dry) 
equivalent to 1000 cc. of the standard ammonia solution. Dry in 
the air bath at 115° to 120° for thirty minutes, cool in a desiccator, 
and weigh. Dissolve in ammonia-free Water in a 500-cc. measuring 
flask. Dilute to exactly 500 cc. Mix well and transfer to a dry 
500-cc. bottle. Label and keep stoppered when not in use. 

1000 cc. standard NHg contains g. N 

Per cent N in (ISrH^)2S04 by theory is 

1000 cc. NH3 is equivalent to g. (NH4)2S04 

Before After 

heating heating 

Weight of crucible + (NHJgSO^ = 

Weight of crucible = 

Weight of (NHJ2SO, 

Per cent dry matter in salt is 

How much of the ammonium sulfate will it be necessary to weigh 
out in order to have exactly 5 g. of the dry salt ? 



30 



PRACTICE XIV 

DETERMINATION OF NITROGEN IN AMMONIUM SULFATE 

Place 10 cc. of the ammonium sulfate solution in a Kjeldahl flask, 
connect in the distillation apparatus, add 10 cc. of the alkali solu- 
tion, and distill into a 300-cc. Erlenmeyer flask containing 10 cc. of 
the standard hydrochloric acid and about 15 cc. of ammonia-free 
water to a volume of 200 cc. Add lacmoid and titrate the excess 
acid with standard ammonia. 

Titrations (1) cc. NHg 

(^) cc. NHg 

Av cc. NHj 

N in 10 cc. of solution mg. 

Per cent N in dry salt 

The percentage purity of the dry salt is 

Does the percentage of nitrogen vary directly or inversely with 
the titration readings ? 



32 



PRACTICE XV 

NITRIFICATION 

Bring 40 cc. of the standard ammonium sulfate solution into a 
500-cc. measuring flask, add 0.3 g. of dipotassium phosphate, 0.5 g. 
of calcium carbonate, and about 2 g. of fresh, rich garden soil, and 
make up to the mark. Mix well and let settle. 

Place 600 g. of clean, washed, and dried white sand in a perco- 
lator. Upon this pour 100 cc. of the above solution in such a way 
as to wet the whole surface of the sand. Allow to stand one hour, 
wash with about 500 cc. of ammonia-free water, collect the wash- 
ings, and make up to exactly 500 cc. Place 250-cc. portions in 
Kjeldahl flasks and determine nitrogen in the usual way. Com- 
pare the amount of nitrogen found with that originally applied in 
the ammonium sulfate. 

Titrations (1) ..cc. NHg 

(2) cc. NH3 

Av cc. NH3 

N found mg. 

Add another 100-cc. portion of ammonium sulfate solution to 
600 g. of clean, washed, and dried sand held in a percolator, cover, 
and allow to stand in a dark place at warm room temperature for 
six weeks, adding water from time to time to prevent complete 
drying. Then wash out and determine the ammonia nitrogen as 
directed above. 

Titrations (1) ....cc. NH3 

(2) cc. NH3 

Av cc. NH3 

N found mg. 

Per cent N nitrified 

What change has been brought about, and how ? Why does not 
all of the nitrogen added appear in the second distillation ? Why 
was the percolator kept in the dark ? Why was K2HPO4 added ? 
CaCOg ? garden soil ? Why was the ammonium sulfate solution 
poured upon sand instead of being left in a flask ? 



34 



PRACTICE XYI 

THE EFFECT OF LIME UPON NITRIFICATION 

Place 500 g. of a worn acid soil in a percolator. Upon this pour 
100 cc. of a dilute ammonium sulfate solution (40 cc. of the standard 
ammonium sulfate solution plus 460 cc. of water). Allow to stand 
one hour, wash with about 500 cc. of ammonia-free water, and deter- 
mine the ammonia nitrogen as directed in Practice XV. 

Titrations (1) cc. NH3 

(2) CC.NH3 

Av '...cc. ISTHg 

N found mg. 

Into one percolator bring a second 500 g. of the worn acid soil, 
and into another a third with which 5 g. of finely ground limestone 
has been thoroughly mixed. To each of these add 100 cc. of the 
ammonium sulfate solution used above, and allow to stand in a dark 
place at room temperature for six weeks. Then wash out and deter- 
mine the ammonia nitroe-en as directed above. 



Without lime- 
stone 

Titrations (V) 


With lime- 
stone 


cc. NH, 


(2) 




cc. NH. 


Av. 




cc. NH. 


N found 




mg. 


Per cent N nitrified 





Explain the effect of the limestone. 
What is one effect of liming worn lands ? 
Does nitrification enrich the soil ? 



36 



PRACTICE XVII 

PREPARATION OF AMMONIUM MOLYBDATE SOLUTION i 

Dissolve 100 g. of molybdic acid in 400 cc. of ammonium hydroxid 
of .96 specific gravity, and pour this solution slowly and with con- 
stant stirring into 1250 cc. of nitric acid of 1.20 specific gravity. 
It is best to cool the acid after the addition of each small amount 
of ammonium hydroxid. Keep the mixture in a warm place several 
days, or until a portion heated to 40° deposits no yellow precipitate 
of ammonium phosphomolybdate. 



PRACTICE XVIII 

PREPARATION OF A STANDARD POTASSIUM HYDROXID 
SOLUTION 1 

In 400 cc. distilled water dissolve the number of grams of the purest 
potassium hydroxid to be obtained, sufficient to make 4 liters of a 
solution, 1 cc. of which will be equivalent to 0.5 mg. of phosphorus. 
Remove carbonates with barium hydroxid, as in Practice VIII. Then 
make up to 500 cc. and titrate two 10-cc. portions with standard 
hydrochloric acid, using phenolphthalein as indicator. Compute the 
exact weight of potassium hydroxid in the remaining solution, and 
dilute with a sufficient quantity of water to reduce the strength to 
exactly 2.0809 g. potassium hydroxid per 100 cc, so that 1 cc. is 
equivalent to 0.5 mg. phosphorus. 

Mix well, check up by again titrating, and label : Standard Potas- 
sium Hydroxid (1 cc. = 0.5 mg. P). 

1 To be done by the instructor. 



38 



PRACTICE XIX 

PREPARATION OF A STANDARD NITRIC ACID SOLUTION i 

Determine the specific gravity of concentrated nitric acid. By 
tlie use of the specific-gravity table calculate the quantity sufficient 
to make 4 liters of solution of the strength equivalent per cubic centi- 
meter to the standard potassium hydroxid solution. Dilute this with 
ammonia-free water to 3.5 liters and titrate two 25-cc. portions of 
the standard potassium hydroxid with the dilute nitric acid, using 
phenolphthalein as indicator. Then add sufficient ammonia-free 
water to make the nitric acid of the same titrating strength as the 
standard alkali. Mix thoroughly and check by another titration. 

1 To be done by the instructor. 



39 



PRACTICE XX 

DETERMINATION OE PHOSPHORUS IN FARM PRODUCE 

Each group of students will work upon one of the following 
products : 

1. Wheat. 5. Oats. 

2. Corn. 6. Oat straw. 

3. Corn stover. 7. Red-clover hay. 

4. Corncobs. 8. Alfalfa hay. 

Weigh out 2 g. of the material in a 25-cc. crucible, moisten with 
a .15 per cent solution of calcium nitrate, dry carefully, and ignite 
in a muffle furnace at a low red heat for two hours. Transfer to a 
250-cc. beaker, digest in about 15 cc. of nitric acid, dilute to about 
40 cc, filter, and wash. Evaporate the filtrate and washings to about 
25 cc, add 5 cc. of nitric acid, just neutralize with ammonia, and 
clear up with a few drops of nitric acid, using heat if necessary, but 
avoiding more than a few drops in excess. Heat to 50°-60° on a 
water bath, add 10 cc. of the clear molybdate solution, stir, keej) 
at 50°-60° for one hour, and allow to stand over night. Filter, wash 
twice by decantation, using 25-cc. portions of cold water, stirring 
thoroughly, and then allowing the precipitate to settle before decant- 
ing upon a 9-cm. filter. Transfer the precipitate to the filter, and 
wash the beaker and filter seven or eight times with small amounts 
of cold water until free from acid. Place the filter containing the pre- 
cipitate in the beaker and add standard potassium hydroxid in 10-cc. 
portions until the precipitate is dissolved. Titrate the excess alkali 
with standard nitric acid, using phenolphthalein as an indicator. 

cc. HNO3 cc. KOH to mg. P Per Cent P 

used dissolve 

ppt. 



Av 

Calculate the results obtained, and record with these the results 
obtained by three members of each group as indicated on the fol- 
lowing page. Value phosphorus at 12 cents per pound. 

How many pounds of steamed bone meal will be required to replace 
the phosphorus removed from the soil in a 100-bushel crop of corn, 
a 100-bushel crop of oats, a 4-ton crop of clover hay, and a 50-bushel 
crop of wheat ? (See Practice V.) 



40 



PRACTICE XX (Continued) 



Name of Student 


Material 


Per Cent P 


Pounds P 
PER Ton 


Value 
PER Ton 
































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 









41 



PRACTICE XXI 

DETERMINATION OF TOTAL PHOSPHORUS IN SOILS 

Each group of students will work upon one stock soil, such as the 
following : 

1. Surface of gray silt loam. 5. Surface of black clay loam. 

2. Subsoil of gray silt loam. 6. Subsoil of black clay loam. 

3. Surface of brown silt loam. 7. Sandy soil. 

4. Subsoil of brown silt loam. 8. Peaty soil. 

Weigh 10 g. of sodium peroxid into a crucible of spun iron or of 
porcelain of about 100-cc. capacity and thoroughly mix with it 5 g. 
of soil. If the soil is peaty, burn off the greater part of the organic 
matter before mixing with the sodium peroxid. If the soil is very 
low in organic matter, add about 0.2 g. of pulverized sugar to hasten 
the reaction. Heat the mixture carefully by applying a flame directly 
upon the surface of the charge and upon the sides of the crucible 
until the reaction is over, and keep at a low red heat for 15 minutes. 
Do not allow fusion to take place. By means of a large funnel and 
a stream of hot water transfer the charge to a 500-cc. measuring flask. 
Acidify with hydrochloric acid, add several cc. of nitric acid, and boil. 
If the reaction has taken place properly, there will be no particles 
of undecomposed soil in the bottom of the flask. Let cool, make up 
to the mark, and shake thoroughly. Allow the silica to settle and 
draw off 200 cc. of the clear solution into a beaker. 

Add ammonium hydroxid until almost neutral, heat to boiling, 
and add ammonium hydroxid slowly in slight excess. Keep boiling 
hot for about one minute, stir, filter through a 15-cm. filter, and 
wash at once with hot water until free of chlorids. Eeturn the pre- 
cipitate to the beaker by means of a stream of hot water, holding 
the funnel over the beaker, and dissolve in hot nitric acid, pouring 
the acid upon the filter to dissolve any precipitate remaining. Evapo- 
rate solution and washings to coTnplete dryness on a water bath, take 
up with dilute nitric acid, heating if necessary, and filter out any 
insoluble silica. Evaporate filtrate and washings to about 20 cc. and 
determine phosphorus according to the directions given in Prac- 
tice XX, using 15 cc. of the clear ammonium molybdate solution. 

cc. HNO3 cc. KOH to . mg. P % P P in 2 mil- 

used dissolve ppt. lion of soil 



Av 

With the above results record those obtained by three members of 
each group, as indicated upon the following page. 

42 



PRACTICE XXI (Continued) 



Name of Student 


Kind of Soil 


Per Cent P 


Pounds of P 
IN Two Mil- 
lion OF Soil 


No. of 100-Bushel 

Crops of Corn 

Equivalent 
































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 









43 



PRACTICE XXII 

SOIL ANALYSIS. DETERMINATION OF TOTAL PLANT FOOD 

Each student will select a soil in wliicb he is especially interested.^ 

1. Dry Matter. 

Weigh out 5 g. of the air-dried soil in a small porcelain dish, dry 
at 100° for five hours, cool in a desiccator, and weigh. 

Weight of vessel plus dry matter 

Weight of vessel 

Weight of dry matter 

Per cent of dry matter 

Av. per cent 



2. Nitrogen. 

Determine according to directions given in Practice IV.^ 

Titrations (1) cc. NH3 

(2) CC.NH3 

Av cc. ISTHg 

Per cent N 

N in 2 million of soil 

1 Collecting Soil Samples. After one has become familiar with the typical boring 
of the soil tyi)e, the sample is collected by taking borings from 10 to 20 different 
places, a rod or more ajjart, each of which should aj^pear to be truly representative 
of the soil type. These borings, thoroughly mixed, should make a trustworthy sample 
for analysis. An auger about li inches in diameter, with the screw point and the 
vertical lips filed off, is the most satisfactory instrument to use. The stem may be cut 
in two and a steel rod of good quality welded to make the auger about 40 inches long. 

Ordinarily, samples may well be taken in sets of three : the surface, or average 
plowed soil (0 to 6| inches) ; the subsurface, or that which can possibly be moved with 
a subsoil plow (6| to 20 inches) ; and the subsoil (20 to 40 inches), corresponding to 
about two million, four million, and six million pounds, respectively, of ordinary soil 
per acre. The surface boring is faade and the hole enlarged about J inch in diameter, 
the soil all being saved. The subsurface boring is then taken and the hole again 
enlarged, but the extra soil is not saved. Finally, the subsoil boring is taken and the 
soil saved from only one half (one groove) of the auger. This provides about equal 
quantities of soil from each stratum. 

Preparation of Sample. The sample of soil after air drying is pulverized to pass 
through a sieve with round holes 1 mm. in diameter. Any gravel which does not 
pulverize as easily as the dried lumps of clay is weighed and its percentage deter- 
mined, after which it is discarded. After thorough mixing, the sample is then placed 
in a tight jar and labeled for analysis. 

2 If for any reason it is thought that the soil contains unusual amounts of nitrates, 
the modified method given in Practice XXIV may be used. 



44 



PRACTICE XXII (Continued) 

3. Total Phosphorus. 

Determine as directed in Practice XXI, reserving the filtrate from 
the ammonium hydroxid precipitate for the calcium and magnesium 
determinations. 

cc. HNO3 cc. KOH to mg. P % P P in 

used dissolve 2 million 

ppt. of soil 



Av 

4. Total Calcium. 

Concentrate the filtrate and washings from the ammonium hydroxid 
precipitate in 3 to about 50 cc. If upon adding a few drops of ammo- 
nium hydroxid a precipitate of aluminum appears, filter, wash, and 
again concentrate to about 50 cc. Add a few drops of ammonium 
hydroxid and enough ammonium oxalate solution to precipitate all 
the calcium and to transform the magnesium from chlorid into oxa- 
late. Digest two hours on the water bath, filter, wash with hot water 
until free of chlorids, dry, and ignite in a weighed crucible over a 
Bunsen burner, finishing to a constant weight over the blast lamp. 

Weight of crucible + CaO 

Weight of crucible 

Weight of CaO 

Weight of Ca 

Per cent Ca 

Av. per cent , 

Ca in 2 million of soil 

5. Total Magnesium. 

Concentrate the filtrate and washings from 4 to about 50 cc, cool, 
add a few drops of ammonium hydroxid, precipitate the magnesium 
by adding slowly, while stirring, microcosmic salt in excess, add 10 cc. 
of ammonium hydroxid, cover, and let stand over night. Filter, wash 
with dilute ammonium hydroxid (1 part of ammonium hydroxid of .96 
sp. gr. to 4 parts of water), dry, and ignite in a weighed crucible over 
a Bunsen burner, finishing to a constant weight over the blast lamp. 

Weight of crucible + MggPjO^ 

Weight of crucible 

Weight of Mg^PgO^ 

WeiQ-ht of Mff 



Per cent of Mg 

Av. per cent 

Mg in 2 million of soil 

45 



PRACTICE XXII (Continued) 

6. Total Potassium. 

Puse 1 g. of soil with 1 g. of ammonium chlorid and 8 g. of cal- 
cium carbonate in a platinum crucible^ according to the method of 
J. Lawrence Smith.^ Transfer the fused mass to a porcelain dish, 
slack with hot water, grind finely with an agate pestle, transfer to a 
filter, and wash with about 400 cc. of hot water. Concentrate the 
filtrate and washings in a Jena-glass beaker to 10 or 20 cc. on the 
water bath, filter, and wash. Acidify filtrate and washings with 
hydrochloric acid, concentrate to about 10 cc, and add 1.5 cc. of 
a platinic chlorid solution, of which 10 cc. contains 1 g. platinum. 
Evaporate on the water bath to a sirupy consistency, cool, take up 
with about 10 cc. of 80 per cent alcohol, filter, wash ten or twelve 
times with 80 per cent alcohol, three times with a solution of ammo- 
nium chlorid (200 g. ammonium chlorid in 1000 cc. of Avater satu- 
rated with platinic chlorid), and again ten or twelve times with 80 
per cent alcohol. Allow the filter to dry thoroughly, and dissolve 
the potassium platinic chlorid in hot water, catching the solution and 
washings in a weighed porcelain or platinum dish. Evaporate to 
dryness on the water bath, heat thirty minutes at 110° in an air 
bath, cool in a desiccator, and weigh. 

Weight of dish 4- KgPtCle 

Weight of dish 

Weight of KaPtCle 

Weight of K 

Per cent of K 

Av. per cent 

K in 2 milhon of soil 



1 The fusion may be made in the iron crucible used for the phosphorus determina- 
tion. Because of the high temperature necessary, however, but four or five deter- 
minations can be made in the one crucible. 

2 Fresenius's " Quantitative Chemical Analysis," 1904, p. 1175. 



46 



PRACTICE XXII (Continued) 

7. Reaction. 

Follow the directions given in Practice VII. 

If acid, determine the acidity according to Practice IX. 

Titrations (1) cc. NaOH 

(2) cc. NaOH 

Av cc. NaOH 

Per cent CaCOg required 

CaCOg required for 2 million of soil 

If alkaline, determine the inorganic carbon (limestone present), as 
indicated in Practice X. 

cc. CO2 

Bar., Temp. 

Weight of C equivalent 

Weight of CaCOg equivalent 

Per cent of CaCOg present 

Av. per cent 

CaCO- in 2 million of soil 



Composition of Soil 

Pounds per Acre 
Air-dry Water-free 

basis basis 



Nitrogen 

Phosphorus 

Potassium 

Calcium 

Magnesium 

Limestone present 

Limestone required 



Suggest a practical method, of unlimited application, by which 
the productive capacity of this soil may be profitably increased 
and permanently maintained. 



47 



PRACTICE XXIII 

DETERMINATION OF NITROGEN IN ANIMAL EXCREMENTS,— 
SOLID AND LIQUID 

Each group of students will work upon one of the following : ^ 

1. Horse excrements. 6. Poultry excrement and fresh 

2. Steer excrements. cow's milk. 

3. Cow excrements. 7. Human excrements. 

4. Sheep excrements. 8. Wheat straw and manger ref- 

5. Swine excrements. use (for bedding). 

Record age and condition of animals and food rations as nearly 
as possible in all cases. 

For solid excrement : Weigh out 10 g. of fresh substance on filter 
paper, placed on a watch glass, and transfer both paper and excre- 
ment to a Kjeldahl flask. 

For liquid excrement: Measure out 10 cc. and place in a Kjeldahl 
flask. Compute weight from specific gravity g. 

Solid Liquid 

Titrations (1) cc. Is^Hg 

(2) CC.NH3 

Av. CC. NHg 

Per cent N ' 

Calculate the results obtained, and with these record the results 
obtained by three members of each group, as indicated upon the 
following page. Value nitrogen at 15 cents per pound. 

10 tons alfalfa hay contain lb. N" 

1 ton fresh cow dung contains lb. N 

How many tons of fresh cow dung would be required to furnish 
nitrogen for 10 tons of alfalfa hay ? 

1 The student is encouraged to add to the required materials some other substance 
which may be of possible importance in his home community, including especially 
any organic refuse occurring in consequential amounts. 



50 



PRACTICE XXIII (Continued) 



Name of Student 


Kind of Manure 


Per Cent N 


Pounds N per Ton, and Value 


Solid 


Liquid 


Solid 


Value 


Liquid 


Value 


















































Average 






























































Average 






























































Average 






























































Average 






























































Average 






























































Average 






























































Average 






























































Average 















51 



PRACTICE XXIV 

DETERMINATION OF NITROGEN IN FERTILIZERS 

Weigh out 0.5 g. of each of the following materials and use 20 cc. 
of standard hydrochloric acid in the receiver. 

1. Ammonium sulfate. 

2. Dried blood. 

3. Sodium nitrate. (Use the Kjeldahl method modified for nitrates. 
With the finely ground nitrate in the Kjeldahl flask mix thoroughly 2 g. 
of salicylic acid. Add slowly, cooling if heat is evolved, 30 cc. of con- 
centrated sulfuric acid and, gradually, about 2 g. of zinc dust ; shake 
thoroughly, and let stand over night. Then add mercury and digest as 
usual. In the distillation use 1.5 times the usual amount of alkali.) 



Titrations 
cc. NHj 


Average Cor- 
rected 


CO. NH3 FROM 

Sample 


Per Cent N 


Value per Ton 

(N 15 (J PER 

Pound) 


1. (a) 
(b) 










2. (a) 
(b) 










3. (a) 

' (b) 











How would the reaction of the soil be affected by the residues 
left by each of these materials when used to supply nitrogen for 
plant growth? 



62 



PRACTICE XXV 

DETERMINATION OF TOTAL PHOSPHORUS IN FERTILIZERS 

Each group of students will work upon one of the following 
materials : ^ 

1. Bone ash. 5. Raw rock phosphate. 

2. Raw bone meal. 6. Acidulated rock phosphate. 

3. Steamed bone meal. 7. Double superphosphate. 

4. Acidulated bone meal. 8. Basic slag phosphate. 

For materials containing more than 9 per cent of phosphorus use 
1 g. ; for lower percentages use 2 g. Ignite in a crucible to destroy 
organic matter when present. Transfer to a beaker and digest in 
15 cc. of dilute nitric acid, using a gentle heat. Transfer to a 250-cc. 
measuring flask, cool, and dilute to exactly 250 cc. Mix well, trans- 
fer to a dry bottle, and let settle. Measure 25 cc. into a beaker and 
determine phosphorus according to the directions given in Practice 
XX, using 35 cc. of the ammonium molybdate solution. 

cc. HNO3 cc. KOH to mg. P % P Pounds 

used dissolve per ton 

ppt. 



Av 

Calculate the results obtained, and with these record the results 
obtained by three members of each group, as indicated in the table 
on the following page. Value phosphorus in 1, 5, and 8 at 3 cents ; 
in 2 and 3 at 10 cents ; and in 4, 6, and 7 at 12 cents per pound. 

1 In addition the student may collect and analyze a sample of some phosphatic 
material which may be of special interest to his home community. (Sample a ton or 
a carload of bone meal or phosphate when bought in the neighborhood, by taking a 
teaspoonful from each of 100 different places in the lot.) 



54 



PRACTICE XXV (Continued) 



Name of Student 


Material 


Total Phos- 
phorus PER 
Cent 


Pounds per 
Ton 


Value per 
Ton 
































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 






































Average 









55 



PRACTICE XXVI 

FIXATION OF BASES IN SOILS 

1. Place a small bunch of glass wool in a percolator, cover with. 
1 cm. of clean sand, and add 100 g. of clay soil. Upon this carefully 
pour 250 cc. of dilute ammonium sulfate solution (50 cc. of the solu- 
tion prepared in Practice XIII, plus 200 cc. of ammonia-free water). 
When percolation ceases, mix the percolate thoroughly and deter- 
mine nitrogen in two 50-cc. portions. 

Titrations (1) cc. NHg 

(2) ^ cc.NHg 

Av cc. NHg 

N per cc. in solution used mg. , 

N per cc. in percolate ; mg. 

Per cent N fixed by soil 

2. Eepeat the experiment, using 200 g. of the same soil. 

Titrations (1) cc. ISTHg 

(2) cc. NH3 

Av cc. NHg 

N per cc. in solution used mg. 

N per cc. in percolate mg. 

Per cent N fixed by soil 

3. E-epeat the experiment, using 200 g. of sand soil. 

Titrations (1) cc. NHg 

(2) cc. ISTHg 

Av cc. NH3 

N per cc. in solution used mg. 

N per cc. in percolate mg. 

Per cent N fixed by sbil 

What class of soil components bring about the fixation of bases ? 

Give the general reaction, and explain fully. What chemical 
elements that are important in soil fertility may be retained in 
this way ? 



56 



PRACTICE XXVII 

FIXATION OF PHOSPHOKUS BY SOILS 

Each group of students will use one stock sbil, such, as the 
following : 

1. Surface of gray silt loam. 5. Surface of black clay loam. 

2. Subsoil of gray silt loam. 6. Subsoil of black clay loam. 

3. Surface of brown silt loam. 7. Sandy soil. 

4. Subsoil of brown silt loam. 8. Peaty soil. 

Dissolve 1 g. of double sxiperphosphate in 500 cc. of water, filter, 
and keep in a stoppered bottle. 

1. Determine the phosphorus in 50-cc. portions of this solution 
by concentrating to 25 cc. and following the directioijs given in 
Practice XX. 

mg. P mg. P per cc. 

of solution 



cc. HNO3 


cc. KOH to 


used 


dissolve 




ppt. 



Av 

2. Dilute 50 cc. of the double superphosphate solution to 300 cc. 
and allow it to percolate through 50 g. of soil held in a percolator, 
as in Practice XXVI. Determine the phosphorus in 100-cc. portions 
of the percolate after concentrating to 25 cc, according to the direc- 
tions given in Practice XX, using only 10 cc. of the ammonium 
molybdate solution. 

cc. HNO3 cc. KOH to mg. P mg. P per 6 cc. 

used dissolve of percolate 

ppt. 



Av 

Per cent phosphorus fixed by soil. 



58 



PRACTICE XXVII (Continued) 

3. Thoroughly mix 5 g. of CaCOg with 50 g. of the same soil, and 
allow a second 50-cc. portion of the double superphosphate solution, 
diluted to 300 cc, to percolate through the mixture. Determine the 
phosphorus in 100-cc. portions of the percolate, as directed above, 
using 5 cc. of the ammonium molybdate solution. 

mg. P mg. P j)er 6 cc. 

of percolate 



cc. HNO3 


cc. KOH to 


used 


dissolve 




ppt. 



Av 

Per cent phosphorus fixed by the limed soil. 



Calculate the results obtained, and with these record the results 
obtained by three members of each group, as indicated in the table 
on the following p^ge. 

Give the general reaction for the fixation. Explain the effect of 
the CaCOg. How was the fixation brought about in the noncalcareous 
soils ? Do soluble phosphates applied on the surface penetrate deeply 
into the soil ? How are phosphates removed from the soil largely ? 



60 



PRACTICE XXVII (Continued) 



Name of Student 


Kind of Soil 


Per Cent P fixed 
BY Soil 


Per Cent P fixed 
BY Soil and Lime 


























Average 












> 


















Average 
























. 






Average 






























Average 




» 




















, 






Average 






























Average 






























Average 






























Average 







61 



APPENDIX 

The following practices are inserted by way of suggestion to 
students who desire to pursue the subject further, and to obtain 
more information in regard to their own soils. Other lines of work 
may be followed out at the discretion of the instructor. 

Those students who are preparing to teach the subject should 
perform these experiments together with all of those (already given) 
marked " To be done by the instructor." 



63 



PRACTICE XXVIII 

PEEPAKATION OF A NEUTRAL AMMONIUM CITRATE SOLUTION 

To 370 g. of commercial citric acid add commercial ammonia (sp. 
gr. .96) until nearly neutral ; reduce the specific gravity to nearly 
1.09 and make exactly neutral, testing as follows : Prepare a solu- 
tion of fused calcium chlorid, 200 g. to the liter, and add one fourth its 
volume of strong alcohol. Make the mixture exactly neutral, using 
a small amount of freshly prepared corallin solution as a preliminary 
indicator, and test finally by withdrawing a portion, diluting with an 
equal volume of water, and testing with cochineal solution ; 50 cc. 
of this solution will precipitate the citric acid from 10 cc. of the 
citrate solution. To 10 cc. of the nearly neutral citrate solution add 
50 cc. of the alcoholic calcium chlorid solution ; stir well, filter at 
once through a folded filter, dilute with an equal volume of water, 
and test the reaction with a neutral solution of cochineal. If acid 
or alkaline, add ammonia or citric acid, as the" case may be, mix, 
and test again, as before. Repeat this process until a neutral reac- 
tion is obtained: Add suificient water to make the specific gravity 
1.09 at 20°. . 



64 



PRACTICE XXIX 

DETEEMINATION OF CITRATE INSOLUBLE PHOSPHOEUS 

Use the same materials and amounts as in Practice XXV. If the 
material is acid, wash the weighed sample on a 9-cm. filter with 
water until free of acid. 

Heat in a water bath 100 cc. of the neutral ammonium citrate 
solution to 65° in a 200-cc. Erlenmeyer flask, loosely stopped with a 
stopper holding a 100° thermometer. When 65° is reached put in the 
sample and shake thoroughly. Place in the bath at 65° and let stand 
for thirty minutes, shaking every five minutes. At the end of thirty 
minutes filter and wash thoroughly with water at 65° until all soluble 
phosphorus is removed (test for soluble phosphorus with 1 cc. of 
ammonium molybdate solution). Transfer the filter and its contents 
to a crucible, dry, and burn off all organic matter. Transfer to a 
beaker, add about 15 cc. of nitric acid, and heat until all phosphorus 
is dissolved. Make up to 250 cc, mix well,- transfer to a dry bottle, 
and let settle. Determine phosphorus in 25-cc. portions, according to 
the directions given in Practice XX. 

cc.HNOg cc.KOHto mg. P %P 

used dissolve 

ppt. 



Av 

In making any calculations, value citrate soluble phosphorus at 
12 cents and citrate insoluble phosphorus at 3 cents per pound. 



65 



PRACTICE XXX 

DETERMINATION OF ORGANIC CARBON IN SOILS 

Place 2 g. of an ordinary soil (or 0.5 g. of a peaty soil), 10 g. of 
sodium peroxid (as free as possible from carbonate), and, depending 
upon the amount of organic matter present, from 0.7 to 1 g. of very 
finely powdered magnesium (to start the combustion) in a Parr^ 
explosion bomb. Close the bomb, mix the contents thoroughly by 
shaking, place bomb in a vessel of water so that only the stem pro- 
jects through -a hole in the bottom of a tin can inverted over the 
vessel of water, and explode by means of a hot iron plug or an elec- 
tric current. Bring the contents of the bomb into a beaker with a 
stream of hot water, boil a few minutes with the beaker covered, 
and, by means of the separatory funnel, bring into the Erlenmeyer 
flask of the apparatus. Liberate the COg with dilute (1 : 2) sulfuric 
acid, boiling finally, measure the volume of the gas, absorb the 
CO2 in a gas pipette containing a 33 per cent solution of potassium 
hydroxid, and measure the unabsorbed gas. Xote the temperature 
and pressure, and calculate the organic carbon. 

cc. of CO2 

Bar., Temp. 

Weight of C 

Weight of C in peroxid 

Weight of total C in soil 

Per cent of total C 

Per cent of inorganic C 

Per cent of organic C 



1 Journal American Chemical Society, Vol. 26, pp. 294, 1640. 



66 



PRACTICE XXXI 

SOIL ANALYSIS; DETERMINATION OF THE PLANT FOOD 
SOLUBLE IN STRONG HYDROCHLORIC ACIDi 

Place 10 g. of the air-dried soil in a 200-cc. Erlenmeyer flask, add 
100 cc. of hydrochloric acid (sp. gr. 1.115), close with a rubber stop- 
per in which is a glass tube 18 inches long, and digest for ten hours 
on a water bath, at the temperature of boiling water, shaking once 
every hour. Dilute, filter through a 15-cm. filter, wash free of chlo- 
rids with hot water, and evaporate filtrate and washings to complete 
dryness after adding 5 cc. of nitric acid to destroy organic matter. 
Take up with about 10 cc. hydrochloric acid and about 25 cc. of 
water, heat thirty minutes, filter, and wash with hot water. Cool, 
make filtrate and washings up to exactly 500 cc, mix thoroughly, 
and put in dry stoppered bottle. Label it Solution A. 

1. Phosphorus. 

Precipitate phosphorus, iron, and aluminum in 200 cc. of Solution A 
with ammonium hydroxid, filter, dissolve precipitate in nitric acid, 
and determine phosphorus in the solution as directed in Practice 
XX, omitting running to dryness to remove silica. 

cc. HNO3 cc. KOH to mg. P % P P in 

used dissolve 2 million 

ppt. of soil 



Av ■ 

1 This is the official method of the Association of Official Agricultural Chemists, 
and is similar to the methods used in other countries. 



67 



PRACTICE XXXI (Continued) 

2. Calcium, and Magnesiuvi. 

Determine these in the filtrate from the ammonium hydroxid 
precipitate in 1, according to the directions given in 4 and 5, 
Practice XXII. 

Weight of crucible + CaO 

Weight of crucible 

Weight of CaO 

Weight of Ca 

Per cent of Ca • 

Av. per cent 

Ca in 2 million of soil 



Weight of crucible + MggPgO^ 

Weight of crucible 

Weight of Mg2P207 

Weight of Mg 

Per cent of Mg 

Av. per cent 

Mg in 2 million of soil 



3. Potassium. 

Evaporate 100 cc. of Solution A to complete dryness in a porcelain 
dish on the water bath. Ignite gently over a Bunsen burner at a 
dull red heat, add a little hot water, and grind very fine with the 
blunt end of a glass rod. Add more water and digest thirty minutes 
on the water bath, filter, wash thoroughly with hot Avater, acidify 
with a few drops of hydrochloric acid, and concentrate on the water 
bath with 1 cc. of platinic chlorid solution to a sirupy consistency. 
Complete the determination as indicated in 6, Practice XXII. 

Weight of dish + K2PtCl6 

Weight of dish 

Weight of KaPtClg 

Weight of K 

Per cent of K 

Av. per cent 

K in 2 million of soil 



68 



PRACTICE XXXII 

SOIL ANALYSIS : DETERMINATION OF THE EASILY SOLUBLE 

PLANT FOOD 

Place 100 g. of air-dried soil in a 2-liter bottle, add 1 liter of 
a 1 per cent citric acid solution, let stand seven days, shaking, several 
times each day, filter off 800 cc, evaporate to dryness finally in a 
small porcelain dish, gently ignite over a Bunsen burner, add 10 cc. 
of nitric acid, evaj)orate to dryness, dissolve in nitric acid, filter, and 
wash with hot water. Make up to exactly 500 cc, mix thoroughly, 
transfer to a dry bottle, and label Solution B.^ 

1. Phosphoi'us. 

Concentrate 200 cc. of Solution B to about 20 cc, and determine 
phosphorus according to the directions given in Practice XX, using 
15 cc. of the clear ammonium molybdate solution. 

cc. HNO3 cc. KOH to mg. P % P P in 

used dissolve 2 million 

ppt. of soil 



Av : 

2. Potasshtm. 

Evaporate 200 cc. of Solution B to complete dryness and deter- 
mine potassium as indicated in 3, Practice XXXI. 

Weight of dish + K2PtCl6 

Weight of dish 

Weight of K^PtClfi 

Weight of K 

Per cent of K 

Av. per cent 

K in 2 million of soil 



^ In order to avoid any difficulty in removing the organic acid, tlie use of one fiftli 
normal nitric acid, as suggested by Peters and Averitt,* or of still weaker nitric 
acid, as suggested by d'Sigmond,! is to be recommended for the extraction of easily 
soluble plant food. 

* Bui'eau of Chemistry, Bulletin 99, p. 115 ; and Bulletin 105, p. 142. 
t Journal American Chemical Society, Vol. 29 (1907), p. 929. 



69 



PRACTICE XXXIII 

DETERMINATION OE THE PLANT-FOOD REQUIREMENTS 
OF A SOIL BY A POT-CULTURE TEST 

Procure sufficient soil to fill a series of ten ordinary four-gallon 
butter crocks. Collect the soil to a depth of 10 inches, keeping the 
first five inches separate from the second five inches. Air-dry the 
soil and fine it so that it will pass through a i-inch mesh sieve. 
Separately mix the two portions very thoroughly. In the center of 
each pot make a drainage hole about ^ inch in diameter, cover this 
with a piece of copper-wire netting, and upon this place a bunch of 
glass wool extending over the hole. Fill each pot to the depth of 5 
inches with an equal weight of the second depth of soil, pressing it in 
firmly to represent as nearly as possible natural conditions of com- 
pactness. With an equal weight for each pot of the first depth of 
soil, which, when thoroughly compacted, will fill the pot within ^ 
inch of the top, mix very thoroughly the kind and amount of material 
or materials, as indicated below, and bring the mixture into the pot. 

Plan fok Pot-Culture Test 



Pot No. 


Materials to be applied 


Grams per Pot 


1 

2 


None 

Dried blood 



15 


3 
4 


Steamed bone meal 

Potassium sulfate 


6 
3 








5 

6 


None 

Blood and bone 



15 + 6 
15 + 3 

6 + 3 


7 


Blood and sulfate. ........ 


8 


Bone and sulfate 






9 
10 


Blood, bone, and sulfate 

None 


15 + 6 + 3 




Plant the series with wheat, oats, timothy, or other suitable crop, 
by removing a layer of the surface soil, distributing the seed, and 
returning the soil removed. A sufficient number of seeds should be 
planted so that a uniform number of strong seedlings may finally 
be left in each pot. (About 20 plants are satisfactory for cereals.) 
Place the series of pots either in a greenhouse or out in the open, 
with arrangements so that they may be protected from severe wind 
or heavy rain. Water as is necessary, preferably with ammonia-free 
distilled water or with very pure rain water. 

When mature the crop should be harvested uniformly, thoroughly 
air-dried, and weighed, afterward separating the grain from the 
straw, in the case of cereals, and weighing the grain. Calculate 
the applications made, and the yields secured, on the acre basis. 

70 



/:U5i <4^' ii 



One copy del. to Cat. Div. 



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